Centrifugal switch



Aug. 23, 1932. z..c. BRADFORD 1,873,180

CENTRIFUGAL SWITCH I Filed Jan.. 18, 1932 Patented Aug. 23, 1

UNITED STATES PATENT OFFICE mm: C. BBADIOBD, OF DAYTON, OHIO, ASSIGNOR TO DELGO PRODUCTS CORPORATION,

OI DAYTON, OHIO, A CORPORATION OE IDELAWABE cmrrmuen. swrrcn Application Med January 18, 1988. Serial No. 587,197.

This invention relates to centrifugal switches and especially to commutator short circuiting devices for alternating current motors particularly motors of the repulsioninduction t pe. ,One kind of commutator short circulting device heretofore devised consistsdf an annulus of coil spring wire surrounding the armature shaft and enclosingla lura'lity of weights which move outwar mm the shaft as its speed increases and cause the convolutions of the spring to engage edges of the commutator segments in order to short circuit the commutator to cause the It is an object of the present invention to overcome the diificulty with respect to spring band commutator short circuiting devices and this object is accomplished by a construc tion wherein the resilient spring band is not 30 permitted to contact directly with the commutator segment but is enclosed within another helical coil annular band of wire of good conducting material. By means of this construction the inner band enclosing the weights and providing the mechanical resistance to outward movement of the weights is not permitted to carry any current and hence is not subjected to deterioration due to sparking. This inner band expands with increase of speed of the motor shaft to cause the convolutions of the outer band to move into engagement with the commutator bars. Al though the convolutions of the outer band may become pitted due to many starting and stopping operations of the motor the short circuiting device remains operable to short circuit the commutator bars at the intended speed.

Further objects and advantages of the I W present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of one form of the present invention is clearly shown. 3

In the drawing:

Fig. 1 is a fragmentary longitudinal view of an electric motor embodying the present invention.

F igs.'2 and 3 are sectional views taken on the line 2-2 of Fig. l showing respectively the short circuiting band in inner and outer positions. F Fig, 4 is a sectional viewof line 44 of ig. 5 is a sectional view of'line 5-5 of Fig. 3.

- Referring to the drawing designates the armature shaft carrying an armature 21 revolving within a field 22'and having its windings connected with the various segments 23 of a commutator. It will be noted that the segments 23 have overhanging portions 24 projecting beyond the non-conducting hub 25 of molded material in which the tangs 26 of the commutator segments are embedded. The hub 25 is molded also to a metal sleeve 27 which is press fitted over the armature shaft 20.

The shaft 20 is provided with a groove 30 which receives a wire .split ring 31' which retains a sleeve 32 which is so shaped and is so related to the hub of the commutator as v to provide an annular pocket 33 for receivin the commutator short circuiting device whic comprises an outer helical coil band 34 of wire of good conducting material surrounding an inner helical coll band 35 of spring wire of resilient material'such as steel spring wire. Before the ends of the wire band 35 are joined together by a threaded connector 36, a number of threaded weights 37 are arranged within the coil of wire 35 before bein bent into annular form.

%[he ends of the band 34.- need not be joined togetherhence the band 34 does not'operate to resist outward movement of the wei hts 37. The ends of the band 35 are join together by the connector 36 in such a manner that the band 35'will-cause the band 34: to rest against the flange 37 of the spring 32 when the motor is at rest. The coils of the bands 34 and 35 are wound in opposite ways so that the turns of the wire will appear to cross each other as shown in Fig.1 In this way the turns of the band 35 when contacting against the inner side of the turns of the band 34, will not be crowded down into the space between the turns of the band 34 and cause them to be wedged therein in such a manner so as to interfere with the operation of the device. By crossing the turns it is apparent that the turns of the wire 35 cannot wedge into the space between the turns of the wire bands 34. Preferabl the band 35 of spring metal wire is woun left hand, and the band 34 of bare soft copper wire is wound right hand.

As the speed of the motor increases the weights 37 move outwardly against the resistance afforded by the band 35 which in turn presses the band 3 linto engagement with the overhanging portion 34 of the segments, of the commutator 23. Then when the speed of the motor decreases the band 35 causes the weights to move inwardly to withdraw the band 3 from contact with the commutator segments. If sparking occurs, only the band 34 will be pitted but this will not iii-- terfere with the operation of the short circuiting device since the cross sectional dimensions of the wire 35 remain unchanged throughout the life of the device.

VJhile the form of embodiment of the present invention as herein disclosed, constitutes' a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is'as follows:

1. A circuit controlling device comprising in combination a shaft, an annular row 0 contacts carried thereby, an expansible annular band of coiled wire of good conducting material coaxial with the shaft and engageable with the contacts, an expansible annular band of coiled spring wire within the first band, and weight members cooperating with the second hand.

2. Acircuit controlling device comprising, in combination, a shaft, an annular row of contacts carried thereby, an expansible annular band of coiled wire of good conducting material coaxial with the shaft and engageable with the contacts, an expansible annular band of coiled spring wire within the first band, and weight members within the second hand.

3. A commutator short circuiting device comprising, in combination, a shaft, :1. commutator carried thereby, a retainer on the shaft and cooperating with' the commutator to provide an annular pocket,- an expansible annular band of coiled wire of. good conpansible annular band of coiled ring wire within the first band, and weig ts withm the second band.

4. .A device according to claim 3 in which one coiled wire band is wound right hand, and the other band is wound left hand.

In testimony whereof I hereto aflix my signature.

- ZERBE C. BRADFORD.

ducting material located-in said pocket and engageable with the commutator, 7 an ex- 

